Which cell phone do you have? As different sets are having different process on same thing. Still you will try one thing i will suggest you-

just go to the message box and select the message you want to delete. May be when you touch the screen for select the message you want to delete, it shows a option "Delete Thread" or "delete". If it is then click on this option. Your message will be deleted. Otherwise please specify first, which cell phone you are using...

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Repairability

Stay in the loop

It's time to speak out for your right to repair

We have a chance to guarantee our right to repair electronic
equipment—like smartphones, computers, and even farm equipment. This is a once-in-a-generation
chance to protect local repair jobs—the corner mom-and-pop repair shops that
keep getting squeezed out by manufacturers.

Join the cause and tell your state representative to support Right to Repair. Tell them you believe repair should be fair, affordable, and accessible. Stand up for your right to repair!